using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using NUnit.Framework;

namespace ProjectEuler.Core
{
    public class Problem11 : IProjectEulerProblem
    {
        protected string rawgrid =
            @"08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
            49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
            81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
            52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
            22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
            24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
            32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
            67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
            24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
            21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
            78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
            16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
            86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
            19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
            04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
            88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
            04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
            20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
            20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
            01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48";

        protected int[,] ParseRawGridInto2dArray(string rawGrid, int size)
        {
            var array1d = Regex.Split(rawGrid, @"\W+");
            var array2d = new int[size,size];

            for (int y = 0; y < size; y++)
            {
                for (int x = 0; x < size; x++)
                {
                    array2d[x, y] = int.Parse(array1d[(y*size) + x]);
                }
            }

            return array2d;
        }

        protected class QuadProduct
        {
            public int[] Number;
            public int Product
            {
                get
                {
                    var product = Number[0];
                    for (int i = 1; i < 4; i++)
                    {
                        product *= Number[i];
                    }
                    return product;
                }
            }
            public QuadProduct()
            {
                Number = new int[4];
            }
            public int x { get; set; }
            public int y { get; set; }

            public override string ToString()
            {
                return Product.ToString();
            }
        }

        protected IList<QuadProduct> FindAdjacentQuadProducts(int[,] grid2d, int size)
        {
            var quads = new List<QuadProduct>();
            for (int i = 0; i < size; i++)
            {
                for (int j = 0; j < size; j++)
                {
                    // southwest
                    if (i >=3 && j <= (size-4))
                    {
                        quads.Add(GetSouthWest(grid2d, i, j));
                    }
                    // south
                    if (j <= (size - 4))
                    {
                        quads.Add(GetSouth(grid2d, i, j));
                        // southeast
                        if (i <= (size - 4))
                        {
                            quads.Add(GetSouthEast(grid2d, i, j));
                        }
                    }
                    // east
                    if(i < (size-3))
                    {
                        quads.Add(GetEast(grid2d,i,j));
                    }
                }
            }
            return quads;
        }

        private QuadProduct GetEast(int[,] grid, int x, int y)
        {
            var quad = new QuadProduct();
            quad.Number[0] = grid[x, y];
            quad.Number[1] = grid[x + 1, y];
            quad.Number[2] = grid[x + 2, y];
            quad.Number[3] = grid[x + 3, y];
            quad.x = y;
            quad.y = x;
            return quad;
        }

        private QuadProduct GetSouthEast(int[,] grid, int x, int y)
        {
            var quad = new QuadProduct();
            quad.Number[0] = grid[x, y];
            quad.Number[1] = grid[x + 1, y + 1];
            quad.Number[2] = grid[x + 2, y + 2];
            quad.Number[3] = grid[x + 3, y + 3];
            quad.x = y;
            quad.y = x;
            return quad;
        }

        private QuadProduct GetSouth(int[,] grid, int x, int y)
        {
            var quad = new QuadProduct();
            quad.Number[0] = grid[x, y];
            quad.Number[1] = grid[x, y + 1];
            quad.Number[2] = grid[x, y + 2];
            quad.Number[3] = grid[x, y + 3];
            quad.x = y;
            quad.y = x;
            return quad;
        }

        private QuadProduct GetSouthWest(int[,] grid, int x, int y)
        {
            var quad = new QuadProduct();
            quad.Number[0] = grid[x, y];
            quad.Number[1] = grid[x - 1, y + 1];
            quad.Number[2] = grid[x - 2, y + 2];
            quad.Number[3] = grid[x - 3, y + 3];
            quad.x = y;
            quad.y = x;
            return quad;
        }

        public int Number
        {
            get { return 11; }
        }

        public string Description
        {
            get { return "What is the greatest product of four adjacent numbers in any direction in the given 20x20 grid?"; }
        }

        public string Answer
        {
            get
            {
                var allQuads = FindAdjacentQuadProducts(ParseRawGridInto2dArray(rawgrid, 20),20);
                var maxProduct = allQuads.OrderByDescending(quad => quad.Product).First();
                return maxProduct.Product.ToString();
            }
        }
    }

    [TestFixture]
    public class Problem11Tests : Problem11
    {
        [Test]
        public void Raw_grid_can_be_processed_into_2d_array()
        {
            var grid = ParseRawGridInto2dArray(rawgrid, 20);

            Assert.AreEqual(20*20,grid.Length);
        }

        [Test]
        public void Grid_contains_the_right_numbers()
        {
            var array1d = Regex.Split(rawgrid, @"\W+");
            var grid = ParseRawGridInto2dArray(rawgrid, 20);

            Assert.AreEqual(int.Parse(rawgrid.Substring(0,2)), grid[0,0]);
            Assert.AreEqual(int.Parse(array1d.Last()), grid[19, 19]);
        }

        [Test]
        public void Works_on_a_small_grid()
        {
            string smallGrid =
                @"00 00 00 99
                                 00 00 99 00
                                 00 99 00 00
                                 99 00 00 00";

            var allQuads = FindAdjacentQuadProducts(ParseRawGridInto2dArray(smallGrid, 4), 4);
            var maxProduct = allQuads.OrderByDescending(quad => quad.Product).First();
            
            Assert.AreEqual(99*99*99*99, maxProduct.Product);
            Assert.AreEqual(3,maxProduct.x);
            Assert.AreEqual(0, maxProduct.y);
        }

        [Test]
        public void answer()
        {
            var ans = Answer;
        }
    }
}